Climatic conditions this year are ideal for fleas, with dogs and cats acting as the ideal hosts during Covid-related lockdowns.


Summer in Australia is often associated with an increase in fleas, but this year in particular the weather has created a perfect storm for severe outbreaks. This is due to the combination of three factors: heat, humidity, and pets living under Covid lockdown conditions. Understanding the flea life cycle is critical for gaining control, especially when infestation levels are high.

The most common species pest managers will encounter is the cat flea (Ctenocephalides felis) which despite its name mostly affects dogs, and in the process impacts humans. It is one of the 88 identified species of flea in Australia (of which 78 are native to the continent and the remaining 10 are introduced species).

In an infestation environment, more than 95% of the fleas will be in the immature stages. Adults (the other <5%) are present feeding off hosts, reproducing by laying and dropping their eggs into the environment. The adult stage is the most active stage, with humans and pets alike often suffering from irritating bites.

Warm weather makes fleas mature more quickly. Consistent heat at or above 30°C is ideal for flea eggs, larvae and pupae. A normal flea cycle from egg to adult takes approximately two months, however with warmer weather – the kind we have experienced this summer – this can be reduced to around three weeks.

Flea eggs and larvae are prone to drying out, so consequently, low humidity can kill fleas. This is one of the reasons that fleas are common along the Australian coast, but not so much as you head further inland. Even if temperatures drop, as long as the weather is humid, the flea life cycle will merely slow rather than stop. With this year’s La Niña weather conditions, Australia will be more humid than usual, creating the ideal conditions for flea eggs and larvae to thrive.

As well as having near-perfect breeding conditions this summer, Covid-related lockdowns have seen many people choosing to adopt pets during their isolation. Dogs and cats are common ‘reservoirs’ for fleas, and an increase in pets has been linked to increases in flea problems.

With ideal conditions for an accelerated life cycle and maximal flea survival, flea numbers can quickly explode. Obviously, homeowners suffering an infestation will be most concerned about treating the biting adult fleas. However, properly breaking the flea life cycle is the best way to provide long-lasting control of this irritating pest.

It all starts with a thorough inspection

Ask your customer about any specific areas where they are noticing activity or are being bitten, for example the lounge room, bedroom, BBQ area, etc. But don’t solely rely on their responses, as there may be areas of activity they haven’t noticed. During the inspection it can be a good idea to wear light-coloured clothing as this will facilitate simple visual identification of fleas and their deposits directly on your clothing.

Inspect all locations where animals feed and sleep, paying attention especially to cracks, skirting, corners, floorboard grooves, edges of walls, wardrobes, backyards, and long grass. Carefully examine all areas where animals rest, including those that are difficult to access. Remember that cats and dogs can sleep behind, in or on top of furniture and other high places, as well as in the subfloor areas of homes on piers. These are prominent areas of egg, larvae and adult harbourages. Larvae are often found in cracks and crevices in the floor, under rugs, carpets, and in the shade beneath vegetation.


The customer takes control of the flea environment

Be sure to advise your customers that for best results, prior to application but after your inspection, they should remove and clean pets, clean and vacuum infested areas, and dispose of waste to prevent fire-infestation. They will need to remove and dispose of any heavily soiled or infested material or bedding.

Once the areas of infestation have been addressed, the rest of the property should also be thoroughly cleaned and vacuumed. Special attention should be given to carpets, rugs, armchairs, upholstered sofas and under furniture, in order to remove eggs, larvae and pupae. Beds, blankets, rugs and other similar items that animals have been in contact with should be discarded or washed in hot water. All vacuum cleaner dust bags and filters should be sealed and disposed of. If using a bagless vacuum cleaner, the waste should be emptied into sealed bags before disposal, and any care or maintenance instructions of filters (e.g. Hepa type filters) should be followed shortly afterwards. In the interest of better hygiene and to eliminate a possible further ongoing problems, it is recommended that filters are replaced.

Suggest to your customer that they take the pet(s) to a vet for washing and a prescribed treatment with specific products that target fleas.


Treating the pest

Pest managers should treat flea harbourages, both internal and external, with an insecticide used at the initial clean out rate for rapid knockdown and maximum residual protection. As Australia’s first ZC formulation, Demand Duo from Syngenta combines two actives to deliver a powerful knockdown and excellent residual control of fleas and a wide range of other pests, and can be used on a number of different surfaces.

Be sure to treat areas known to harbour fleas, including outdoor kennels. Remember pets must not have contact with an insecticide-treated surface until it has dried, as described on the label. Perimeter treatments around structures can also reduce flea breeding outdoors. Cutting long grass and wetting down dusty soils before exterior treatments is strongly recommended.

Around 24 hours post treatment, ask your customer to disturb/vibrate surfaces around their house. To do this, the customer simply needs to be active inside their home – for example make noise, turn on radio or TV, walk around normally or even jump and stomp on floors both inside and outside the home, and return any treated pets to the environment. The vibration will cause any developed pupae to hatch and all this activity provides a source of body warmth and carbon dioxide in the house, which encourages the remaining dormant and hiding fleas to become active. They will therefore engage with the treated areas and pets – as well as the active ingredient – in and around the customer’s home.

The fleas can take 1-4 weeks to develop inside their pupae, which protects them from chemical treatments. It is important to explain to customers that fleas may continue to emerge for a couple of weeks after treatment, but that they will then be controlled by the residual treatment.

The properties of this pupal stage is one reason why treatments on rental properties sometimes fail, especially if a flea treatment is completed and the property remains vacant for a couple of months. When the new tenants move in, often with untreated pets, their movement and disturbance within the property triggers the dormant fleas and eggs and a new outbreak from the original infestation occurs.

Tackling a flea infestation with a dual mode-of-action insecticide such as Demand Duo means the irritation caused by the initial adult flea population will be controlled upfront and will continue to be controlled as the flea life cycle continues. For a complete IPM treatment program, it is recommended to use an IGR alongside the insecticide, as this will inhibit the fleas’ transformation from one life stage to the next. Taking control of the whole flea life cycle is the most effective way to tackle the flea problems brought about by recent favourable conditions.